High-vacuum device for heating bodies



Feb. 1927.

8 J. E. 1 11 |ENFE|.D

HIGH VAUUM DEVICE FOR HEATING BODIES Filed Sept. 5, 1921 'Patented Feb. 8, 1927.-

',UNITED STATES PATENT orifice..

j JULIUs n. LILmNrnLD, or KEWd GARDENS, LONG IsLAND, NEW Yoan.

HIGH-VAUM DEVICE FOB HEATING IBOIDIIES.v

Application led September 3, 1921, Serial No. 498,892, and in Germany January 13, 1920.

incandescence for purposes of illumination.`

Or, while constructing any electronic device, such as an X-ray tube, ampllfier or the like, a heating of some of the metal parts may be required in order to free them of occluded gases and to obtain ahlgh vacuum.

Or in such high vacuum devices the heat-'- ing of a metal to its point of volatili za tion may be necessary in order to sputter 1t and improven the'vacuum due to the absorptive properties of volatilized metal: Or, sometimes the soldering of a metal 1s to be per' formed under exclusion of gas, for instance,

`the soldering of tantalum which is very sen? sitive even tominute traces ofy hydrogen.

Sometimes the welding of a metal under such conditions is made advisable or necessary. It is the object of this invention to vide a method of and means for heating odies ina high vacuum.

The idea of using the cathode beam started from a glowing cathode for the purposesabove referred to lies near and it is posslble that many years ago the cathode beamof a gas-filled tube has been tried. Glowing cathodes, however, are very inconstant and susceptible to rapid deterioration. Much worse is the ionic discharge. -1

The present invention is based on the observationthat the discharge from. an actlve cathode surfaceofa small radius of curvature other than a hot filament or hot cathode in general i. e; without application of a separate source of heat can be very successful y used for these purposes if the object to be heated is placed as an anode a small d istance-f-about 10 mm. or less, from the cathode.

For a full understanding of the invention' vreference is had to the accompanying drawings in which- Fig. 1 is a more or less diagrammatic view showing the application of the invention for the production of light;

Fig. 2 is a fragmentary sectional view .of

a detail involving al modification of thev arf rangement',4 shown in Fig. 1; Fig. 3 is afragmentary view showing the application of the invention to high vacuum devlces for freeing the cathode from gas;

Figs. ltand 5 are more or less diagrammatic views showing the application of the invention for volatilizing metal in atube to improve the vacuum In Fig. 1, M represents a preferably conil cal metal body of tantalum, tungsten o1' uranium surrounded by a flat ring R of similar material. the distance between the inner edge of the ring R and the surface of Ythe body M being of the order of 1 mm.A

The body M is` mounted on a rod M1 and the ring' R on a rod R1. The elements de-` scribed are enclosed in the evacuted envelope E through which the wires M2 and R2 connecting the electrodes to a suitable source of alternating current are sealed.

It is understood that instead of the ring lRany otherl body may be used provided it defines edges or points in similarlrelat-ionship tothe body M. In operation the body M isl heated to glowing condition by electronic bombardment from the ring R the inside curvature of which defines the cathodically active edge. It thereby liberates electrons which in turn may strike the ring R and heat it. To avoid this heating it is necessary to rectify thealternating current or to introduce a valve or asymmetric conductor 'into' the circuit. When the device is thus operated with pulsating direct current, it constitutes lan excellent source of intense light for projecting purposes. y

In place of pulsating currentr may of course be used high-tension direct current rso whenever it is available.

The arrangement just described is specialy ly useful for producing a point-like source of light of highintensity.

1f, however, such a character ofthe, light is not essential, a device'may be constructed o for operation with valternating current so that both electrodes may be heated to incandescence. As previously pointed out, in

the device shown in Fig. 1 both electrodes A.

would be heated to incandescence if no valve.

or other rectifying element were used. However, an arrangement more suitable Yfor operation wlth alternatmg current is shown in Fig. 2 in which -Ms has the form of a beveled disk and R3 is a ring having an inwardly beveled ed e. The device maybe connected to a suitab e high-tension circuit and in case the potential difference is not directly suitable, step-up or step-down transformers may and the cavity therein, res ectively. E, is

be used as 1s well understood.

' In Fig. 3, D represents the target of a high-vacuum X-ray tube having a cavity D1 at the place of the focal spot. The cathode -is a rod terminating in a pointed cnd A.

l The rod approaches the target at a vright angle and the end A is turned laterally into the cavity to obtain a more effective light cone.

' 4To make the heating of the cathode feasible, an auxiliary electrode'H provided with cathodically active `points is attached to the anode. ile .there is some latitude in the arrangement for carrying` out the object, I

prefer to form the auxiliary cathode H of lthin foil of tantalum or molybdenum attached to a rod J. The discharge edge of the foil -is provided with saw teeth-like points extending more or less parallel to the end A of the cathode. The rod is loosely mounted in the eyes of projections J1 on the target 'and has at its upper end an enlargement J 2 to prevent its falling'out. During evacuation the foil H which resembles generally the form of a flag, is turned toward the cathode.

operative position by inverting the bulb and allowing the rod J to slide back along the stem of the anode where it may be fixed in an suitable way, no particular means being s own. The rod J can be made to turn so as to swing the ilagaway from the anode.

. t By this arrangement the `cathode A can 'be temporarily made the anode during 4.evacuation and by means of an electronic bombardment fromv the electrode H used temporarily as thecathode can be heated to white heat so as to remove every 'trace of gas therefrom during the pumping operation and after the evacuation is complete, the auxiliary cathode H can be readily brought into va neutral orinactive position. It is under- Astood that for this operation the negative The parts described are contained in a separate bulb in communication with the high-vacuum tube proper (notshown).

In Fio. 5 the cathodically active point C,L is 'attached lto the conductor G leading to lone of the electrodes of the high-vacuum tube. Bi and K1 are the auxiliary electrode When the exhaustion is accom-A` pllished, the flag can be moved out of its lusefulfOr. high vacuum devices in a protective quartz cap an 'Fand 'F1 are protective metal disks. The rtion of the glass neck is enlarged to provide the volatilization chamber N and the openings S afford access of the residual gas in the'main tube into the volatilization chamber to be absorbed by the metallic vapors.

The difference between the forms shown in Fig. 4 and Fig. 5 consists only in the' relation of the vaporizing device to the main tube. While according to Fig. 4 the device is constructed independently of the electrodes. of the tube whose vacuum is to be maintained, in Fig. 5 the connection to one of the electrodes of the'tube has been modified to provide a cathodically active edge or point to bombard the metal to be volatilized.4

y It may be mentioned here that high-vac- ,uum devices ofthe type which are operated by a flow of electrons from a cathodic active surface of a small radius of curvature never operate satisfactorily vunless provisions are made for absorbing gases developed after the high-vacuum tubes are sealed off from the.

pump. y

In theforegoing I have specically referred to several forms of devices whereby metallic parts or bodies may be effectively heated by electronicbombardment .from a cathodically active point, to .produce different effects and results.

It is understood that by suitable changes of detail and the proper selection of auxiliary parts the principle on which the in-l vention is based may be a plied for.. various other purposes. In the I have made reference to welding. The iierence between the operations for carrying out vol- *e atilization and welding or soldering respeci tively involves only adiierence inthe temperature to which the metals acted upon are heated. e

For the sake vof simplicity I have separately referred to the use of a cathodically active' element for heating a cathode or other metallic part in the tube and volatilizing a metal respectively. It should be, noted, however, that both operations may and-are intended to be carried out in connection with the same tube. Each contributes toward improving the vacuum in the tube. Y

' While improvement of the vacuum by means of the volatilization device may be (hot cathode tube, Coolidge tube etc it is for practical commercial purposes absolutely indispensable in connection with tubes operating on the principle disclosed in my apgeneral'.s 12

plie-ation Serial No. '364,215 Iiled Marc 8,

I claim l Il. A-n electron discharge device of the high-vacuum type characterized by the combination with the electrodes, of means elec-A" trically connected with one of the electrodes for improving the vacuum within the tube, said means comprising an auxiliary electrode constructed to act as cathode in close proximity to a part of the other electrode.

2. An electron discharge device otl the high-vacuum type characterized by the coinbination with the normally-operative electrodes, of auxiliary means in electric connection with one ot the electrodes for improving the. vacuum within the tube, said means comprising a cathodically active point and means whereby said auxiliary means may be shifted from a position where the cathodieally active point is in close proximity to a part ot' the other electrode to a position remote from the other electrode.

3. In a high-vacuum tube, the combination with the normally-operative electrodes, of auxiliary means in lelectric connection with the anode for improving the vacuum within the tube, said means comprising a cathodically active point relatively to the cathode and means operative at will to bring the said eathodically active point into close proximity to the cathode and to remove it therefrom.

4. In apparatus of the character described, the combination with a high-vacuum tube and electrodes therein, of means for improving the vacuum within the tube, said means comprising an auxiliary electrode having a small radius of curvature in elose'proximity to one of the said electrodes, and means for producing a potential difference between the auxiliary electrode and the said electrode.

5.,' In apparatus ot the character described, the combination with a high vacuum tube and electrodes therein, of means for improving the vacuum within the tube, said means comprising au auxiliary electrode 'having a small radius of curvature in close proximity tothe cathode, and means for producing a potential difference between the auxiliary electrode andthe cathode.

6. Apparatus according to claim 5 in. which. the auxiliary'electrode is shiftable t0 an inoperative position.

7. In apparatus of the character described, the combination with a high-vacuum tube and electrodes therein, of an auxiliary electrode having a sharp edge in close proximity to one ot' said electrodes and means for producing a potential diiierence between the auxiliary electrode and the said electrode.

8. Apparatus ,according to claim 5 in which said auxiliary electrode consists of a refractory metal oil.

9. Apparatus according to claim 5 in which the edge of the auxiliary electrode is serrated.

In testimony whereof, I aiiix 'my signature.

JULIUS E. LILIENFELD. 

